Quinoa protein-dextran conjugates as functional stabilizers for curcumin-loaded Nanoemulsions

This study employed high-pressure microfluidization (HPM) to facilitate the Maillard reaction between quinoa protein (QP) and dextran (DX), systematically examining the effects of various pressures on the conjugate's physicochemical properties. Fourier transform infrared spectroscopy confirmed the formation of QP-DX conjugates, characterized by a new peak at 1149 cm^-1 (covalent CN bond). Secondary and tertiary structure analyses revealed that HPM-assisted Maillard reaction partially unfolded QP molecules, enhancing conformational flexibility and interfacial properties. The QP-DX conjugate fabricated at 150 MPa demonstrated the highest grafting efficiency, interfacial activity, and smallest particle size within the studied HPM pressure range (50-200 MPa). These conjugates were further applied to stabilize curcumin-loaded nanoemulsions, effectively enhancing their storage and creaming stability compared to that of QP. In vitro digestion tests illustrated that the 150-QP-DX stabilized nanoemulsions exhibited the highest curcumin bioaccessibility (46.42 %) and the most favorable digestion characteristics in the simulated mouth, stomach and intestine environments. This study highlights the potential of HPM-assisted Maillard reaction to enhance QP functionalities, providing a practical strategy for developing high-performance nanoemulsions for bioactive compound delivery. These findings may support the development of plant-protein-based functional foods and nutraceutical formulations with improved stability and bioavailability of active ingredients.